Electrical Flashcards
What are the AC generators rated at?
115 volt, 400 hertz, 3-phase
What are the electrical system’s 3 distribution systems?
- ) AC Power Distribution
- ) DC Power Distribution
- ) Emergency Power Distribution
What changes AC to DC power?
Transformer-Rectifiers
Is the emergency power distribution system part of the normal electrical power distribution system?
Yes, it uses both AC and DC power
In the event of loss of normal AC and DC power, what is the emergency power distribution system powered by?
Aircraft Batteries
Where does the Ground Service Bus receive power from?
Right Generator Bus, APU, or External Power
What are the 4 types of generator faults?
Over or Under Voltage
Over or Under Frequency
What is needed for the battery charger to work?
Batter charger must “BEG” to get powered:
B- Battery switch must be on
E- Emergency Power switch must be off
G- Ground Services Bus must be powered
Items on the Battery Direct Bus
BRACES:
B- Battery Relay
R- Refueling Panel (Ground) and Valves
A- Aircraft Clock
C- Charger and Transfer Relay
E- Emergency DC Bus/Emergency Inverter
S- Stairs Forward (not installed on our fleet)
Items on the Battery Bus (Batt ON)
Triple A's D's: A- APU Control A- APU EGT A- AC Emergency Bus off light D- DC Emergency Bus off light D- DC Transfer Bus off light (OAP only)
Major Items on the Left Gen Bus
PHANG: P- Pack Fan Left H- Hydraulic Aux Pump A- AC Bus Left N- Normal Pitch Trim (Primary-Motor) G- Galley Power
Major Items on the Right Gen Bus
P-GAG: P- Pack Fan Right G- Ground Services Bus-> Batt Charger & Rt T/R A- AC Bus Right G- Galley Power
“EXT PWR AVAIL” light means what?
Correct phase supplied and at least 95 volts
DC Transfer Bus Pwr Supply priority:
- ) Left DC Bus
- ) Right DC Bus
- ) Aircraft Battery
- ) Ground Service Bus (Rt Gen Bus not powered)
What is considered a System Fault?
GPS:
G- Generator Bus fault (Short)
P- Phase imbalance
S- Supply Feed fault (short between Gen and Bus)
Items on DC Transfer Bus (Batt ON):
SAFES*:
S- Start Pump DC (Fuel)
A- APU Door Control
F- Fire Protection & Detection + Master Caution/Warning
E- Eng Start switch & Eng Start Valve
S- Standby Horizon
* Left EOAP
AC Power Source Priority:
- ) Respective Eng Gen
- ) APU Gen
- ) External Power
- ) Operating Gen through the AC Crosstie Relay
Items remaining while on Emergency AC
Captain Navigates and controls Heat
ADI/PFD, HSI/ND, VSI, Altimter, F/O Compass, #1 NAV, #1 CADC, #1 Symbol Generator, Manual Temp Control
Items remaining while on Emergency DC
Crew talks, breathes, and can see heat #1 Comm, #1 Glideslope, P.A., Interphone, Stby Lights, Air Conditioning flow and pressure valves, Cpt's Pitot Heat, EGT
What happens in the event of a system fault?
The GCR, GR, and ACTR will all open. This will isolate the respective Gen Bus and AC Bus from any power source.
What annunciators will illuminate with a system fault?
L/R GEN OFF, L/R AC BUS OFF, DC BUS OFF, AC CROSSTIE LOCKOUT
How many batteries does the electrical system have? Volts?
Two 14 volt NiCad batteries connected in series = 28 volts
How long will emergency power supply the system?
30 minutes minimum
Which buses will remain powered while on emergency power?
- ) AC Emergency Bus
- ) DC Emergency Bus
- ) DC Transfer Bus
- ) Battery Bus
- ) Battery Direct Bus
Where does the AC Emergency Bus normally get its power from?
The left AC Bus through the AC Emergency Power Transfer Relay (AEPTR)
Where does the DC Emergency Bus normally get its power from?
The left DC Bus through the DC Emergency Power Transfer Relay (DEPTR)
When will the DC Transfer Bus be powered by the batteries?
With the:
1.) BATT Switch- On
- ) AC Ground Service Bus- Not powered
- ) Neither DC Bus powered
Which system does AEPTR and DEPTR normally connect to? What about in a failure?
Left electrical system
In a failure of the left system it’s spring loaded to the right
Other than operating on battery power, what else will happen with the EMER PWR switch ON?
- EMER PWR IN USE light illuminates
- cabin standby lights illuminate
- output of the battery charger is disconnected from the batteries
What is a CSD? What does it do?
Constant Speed Drive, it allows the generator to operate at a constant speed independent of engine RPM
What will the CSD DISC Switches do?
Will disconnect the CSD from the engine drive assembly provided the engine N2 RPM is above 25%
What does the L/R Gen switch Reset do?
Resets the Generator Control Relay (GCR)
On the Ground Service Electric PWR panel, what happens if both the APU PWR and EXT PWR switches are selected to ON?
They cancel each other out and neither will supply PWR.
